From b0b277525cb4e476deb461de1b5827a33daa2086 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Tue, 29 Oct 2019 05:47:18 -0700
Subject: [PATCH] core/asm: assembly parser label fixes (#20210)
* core/asm: Fix encoding of pushed labels
EVM uses big-endian byte-order, so to pad a label value to 4 bytes,
zeros must be added to the front, not the end.
* core/asm: Fix PC calculations when a label is pushed
Incrementing PC by 5 is only correct if the label appears after a jump,
in which case there is an implicit push. When it appears after an explicit
push, PC should only be incremented by 4.
* core/asm: Allow JUMP with no argument
This way, a label can be pushed explicitly, or loaded from memory to
implement a jump table.
---
core/asm/compiler.go | 13 +++++--
core/asm/compiler_test.go | 71 +++++++++++++++++++++++++++++++++++++++
2 files changed, 81 insertions(+), 3 deletions(-)
create mode 100644 core/asm/compiler_test.go
diff --git a/core/asm/compiler.go b/core/asm/compiler.go
index c7a544070..799709929 100644
--- a/core/asm/compiler.go
+++ b/core/asm/compiler.go
@@ -57,6 +57,7 @@ func NewCompiler(debug bool) *Compiler {
// second stage to push labels and determine the right
// position.
func (c *Compiler) Feed(ch <-chan token) {
+ var prev token
for i := range ch {
switch i.typ {
case number:
@@ -73,10 +74,14 @@ func (c *Compiler) Feed(ch <-chan token) {
c.labels[i.text] = c.pc
c.pc++
case label:
- c.pc += 5
+ c.pc += 4
+ if prev.typ == element && isJump(prev.text) {
+ c.pc++
+ }
}
c.tokens = append(c.tokens, i)
+ prev = i
}
if c.debug {
fmt.Fprintln(os.Stderr, "found", len(c.labels), "labels")
@@ -181,6 +186,8 @@ func (c *Compiler) compileElement(element token) error {
pos := big.NewInt(int64(c.labels[rvalue.text])).Bytes()
pos = append(make([]byte, 4-len(pos)), pos...)
c.pushBin(pos)
+ case lineEnd:
+ c.pos--
default:
return compileErr(rvalue, rvalue.text, "number, string or label")
}
@@ -201,8 +208,8 @@ func (c *Compiler) compileElement(element token) error {
case stringValue:
value = []byte(rvalue.text[1 : len(rvalue.text)-1])
case label:
- value = make([]byte, 4)
- copy(value, big.NewInt(int64(c.labels[rvalue.text])).Bytes())
+ value = big.NewInt(int64(c.labels[rvalue.text])).Bytes()
+ value = append(make([]byte, 4-len(value)), value...)
default:
return compileErr(rvalue, rvalue.text, "number, string or label")
}
diff --git a/core/asm/compiler_test.go b/core/asm/compiler_test.go
new file mode 100644
index 000000000..ce9df436b
--- /dev/null
+++ b/core/asm/compiler_test.go
@@ -0,0 +1,71 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package asm
+
+import (
+ "testing"
+)
+
+func TestCompiler(t *testing.T) {
+ tests := []struct {
+ input, output string
+ }{
+ {
+ input: `
+ GAS
+ label:
+ PUSH @label
+`,
+ output: "5a5b6300000001",
+ },
+ {
+ input: `
+ PUSH @label
+ label:
+`,
+ output: "63000000055b",
+ },
+ {
+ input: `
+ PUSH @label
+ JUMP
+ label:
+`,
+ output: "6300000006565b",
+ },
+ {
+ input: `
+ JUMP @label
+ label:
+`,
+ output: "6300000006565b",
+ },
+ }
+ for _, test := range tests {
+ ch := Lex([]byte(test.input), false)
+ c := NewCompiler(false)
+ c.Feed(ch)
+ output, err := c.Compile()
+ if len(err) != 0 {
+ t.Errorf("compile error: %v\ninput: %s", err, test.input)
+ continue
+ }
+ if output != test.output {
+ t.Errorf("incorrect output\ninput: %sgot: %s\nwant: %s\n", test.input, output, test.output)
+ }
+ }
+}
--
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